Switching in wave guide transmission system



1947. I w. D. HERSHBERGER 5, 4

SWITCHING IN WAVE GUIDE TRANSMISSION SYSTEM- Filed Feb. 25, 1943 E iq iiI/ "gll Patented Feb. 4, 1947 SWITCHING IN WAVE GUIDE TRANSMISSIONSYSTEM William D. Hershberger, or to Radio Corporatio tion of DelawarePrinceton, N. J assignn of America; a corpora- Application February 25,1943, Serial No. 477,176

Claims. (01. 178-44) This invention relates generally to ultra-highfrequency wave transmission systems and more particularly to switchingmeans for ultra-high frequency wave guides. A

The instant invention is an improvement upon the device described inapplicant's U. S; Patent 2,189,549, granted February 6, 1940, whichdiscloses a thermionic tube circuit for providing switching inconcentric high frequency transmission lines.

Positive switching in wave guide ultra-high frequency transmissionsystems is especially use- I ful in systems employing branched waveguides which are connected to corresponding load devices. For example, abranched wave guide transmission system may be connected to a pluralityof ultra-high frequency radiators which are energized alternately orsuccessively by switching the wave guides in the transmission circuit.

The apparatus disclosed in detail hereinafter provides means forinserting effectively a substantially infinite impedance in one branchof a branched wave guide transmission system to close this branch, whileat the same time permitting substantially unimpeded transmission of theultra-high frequenc waves in the other branch of the wave guide system.The insertion of an infinite impedance is meant herein to comprise theinsertion of a wave reflecting or wav attenuating device to prevent wavetransmission beyond the point of insertion in the guide. The commoncharacteristic of all of theswitching systems disclosed herein is thinsertion of a substantially infinite impedance at a point which issubstantially an integral number of half wave lengths in the guide atthe operating frequency along the selected wave guide branch from thejunction thereof with the remainder of the wave guide transmissionsystem. A high impedance thus placed provides reflections whicheffectively present a similar substantially infinite impedance at thejunction of the branched wave guides.

Among the objects of the invention ar to provide an improved method ofand means for switching ultra-high frequency waves in a wave guidtransmission system. Another object is to provide an improved method ofand means for selectively switching guide waves in a branched wave guidetransmission system. A further object is to provide an improvedmethod'of and means for guiding waves alternately through separatebranches of a branched wave guide transmission system to apply energy toseparate load devices. Another object is to provide an improved methodof and means for inserting substantially infinite impedances in abranched wave guide transmission system at points which aresubstantially integral numbers of halfwave lengths in the guide at theoperating frequency from the branch point of the wave guide system.Another object is to provide an improved high impedance device for awave guide transmission system which comprises a resonant aperture whichmay be ionized selectively upon the application of an externally derivedvoltage. A further object is to provide an improved substantiallyinfinite impedance device for insertion in a wave guide transmissionsystem which comprises a resonant chamber including an ionizing devicefor ionizing selectively a portion of the resonant chamber and aperturedevices for controlling the coupling between the wave guide and theresonant chamber to control effectively the selectivity 1 thereof.

The invention will be described in greater detail by referenc to theaccompanying drawing of which Figure 1 is a schematic plan diagram ofone embodiment thereof; Figure 2 is a sectional view of Figure 1; Figure3 is a schematic diagram of a second embodiment of the invention; Figure4 is an elevational view of a, resonant aperture device utilized inFigure 3; Figure 5a. is a fragmentary elevational view of a thirdembodiment of the invention, Figure 5b is a fragmentary elevational viewof a modification of Figure 5a, and Figure 6 is an equivalent circuitdiagram for the device of Figure 5. Similar reference numerals areapplied to similar elements throughout the drawing.

Referring to Figure 1, a. transmitter l which may, for example, consistof a magnetron oscillator, is coupled in any conventional manner to oneend of a first wave guide 2. The remaining end of the wave guide 2terminates in two branched wave guides 3 and 4. .The remaining endsv ofthe branched wave guides 3 and 4 may b terminated in load devices, suchas antennas or the like which are not shown. A flat vane 5 is pivoted ona shaft 6 to be inserted transversely through a slot I in thefirstbranched wave guide 3 or a slot 8 in the second branched wave guide4. The slots I and 8 are preferably located any integral number of halfwave lengths at the operating frequency from the junction with the firstwave guide 2. Preferably the slots should be only slightly wider thanthe thickness of the vane 5. The vane i may be semi-circular asindicated in Figure 2 and equipped with stops to providev pled to asimilar first wave guide l alternate interruption of either wave guidebranch.

Figure 3 includes a similar transmitter l con- 2 which terminates inbranched wave guides 3 and 4. The open ends of the wave guides 3 and 4may be coupled to any suitable load devices, not shown.

First and second resonant aperture devices il i and I2 are'inserted inthe branch wave guides 3 and 4, respectively at points which arepreferably an integral number of half wave lengths at the from thejunction of the with the first wave guide 2. devices Ii and I2 willbeoperating frequency branch wave guides The resonant aperture describedin detail hereinafter. They are connected through switches l3 and I4respectively to a keying generator or other source of high potential IS.The keying voltages thus applied to the resonant aperture'devices causeionization of the gas in the narrow aperture therein which therebyintroduces a substantially infinite impedance in the branch wave guideat that point. when no ionization of the gas in the resonant aperturedevice occurs, substantially unimpeded wave transmission through theresonant aperture is provided. v

Referring to Figure 4, the resonant aperture devices H and I2 of Figure3 comprise two complementary conducting elements 2|, 22 which areinsulated from each other by transverse insulating members 23, 24. Thecomplete unit is supe ported by any suitable clamping member 23. Thesize and shape of the aperture 23 formed by the complementaryconformations of the conducting members 2|, 22 determines the frequencyat which the aperture resonates. The device may be considered to consistof two highly inductive elements 2i, 22in series with a capacitor formedby the fiat faces 21, 23 which are separated by a narrow air gap 23. Itis this narrow air gap 23 which is ionized by the keying voltage derivedfrom the keying generator l5.

Referring to Figure 5a, a section of the branch wave guide 3, forexample, includes a resonant chamber'34 instead of the resonant aperturedevice l I shown in Figure 3. The resonant chamber 34 includes first andsecond fixed aperture stop devices 35 and 33 disposed transversely withrespect to the wave guide 3.' The resonant chamber 34 should preferablybe tuned to resonance by means of a tuning screw 31 which is adJusted bya tuning knob 38. The walls of the resonant chamber 34 are bentoutwardly to support a gaseous discharge tube 39 in a position whichpermits a small portion of the gas containing envelope to be within theresonant chamber. If the guide 3 is conveying a wave of the H01 type,and the guide is rectangular in cross-section, the flared out portion 45is excited in its E0 mode. That is,

the resonant cavity behaves as a transformer for guided waves to convertHm waves into either E0 waves leaving by the guide section 45 or Hmwaves leaving the cavity 34 by the aperture 36. The aperture 35 is theinput aperture. The guide section 45 is then preferably operated as acut-ofl guide for E0 waves. Coupling between the lamp 33 and the cavity34 then is varied in a simple and effective manner by varying thepenetration. of the lamp 39 in the section of cut-off guide 45.

The gaseous discharge tube 33 should be so located that no ionizationtherein occurs due to the normal wave transmission through the resonantchamber 34. The electrodes of the gaseous discharge tube are connectedthrough a switch 43 to a source of high potential 4|. when the 75 waveguide,

- -4 switch 43 is closed, ionization occurs within the gaseous dischargetube 33 and the ionized portion of the tube within the resonant chamber34 changes the resonant characteristics thereof snfiiciently to offer asubstantially infinite impedance to the. waves transmitted through thesystem. The selectivity of the system is greatly enhanced by selecting asuitable aperture size in the aperture devices 33, 33.

The equivalent electrical circuit for the device described in Figure 5ais shown in Figure 6 whereby the inductances 42 and 43 and thevaricircuit so that the impedance of this circuit viewed at the inputterminals becomes highlyreactive at the operating frequency.

It should be understood that the device of Figure 5:: may be substitutedfor both of the resonant aperture devices of Figure 3, and that thegaseous dicsharge tubes of each resonant cham# ber device may be ionizedby any suitable external voltage source.

It should also be understood that therresonant' characteristics'of theresonant chamber device 34 may be changed by electronic or mechanicalmeans which are actuated by the keying element. Such expedients forvarying the resonantcharacteristics of resonant chambers are wellknownin the art. An example of suchan expedient, shown in Figure 5b, is theperiodic introduction in the resonant cavity of a cylindrical plug 41 ofmetal or dielectric material, such as styrol, having low losses and ahigh dielectric constant with respect to air. To be most eflective thismaterial is introduced in the cavity at a high potential point such asis occupied by the lamp 38 in'Figure 50.

Thus the invention described comprises a new and improved method of andmeans for switching guided waves in a wave guide ultra-high frequencytransmission system.

I claim as my invention:

1. In combination, a. first ultra-high frequency wave guide, means forintroducing ultra-high frequency waves into said first guide,- secondand third wave guides connected in branched operative relation to oneend of said first waveguide,

first wave switching means comprising a first resonant aperture devicein said second wave guide disposed substantially an integral number ofhalf wave lengths in the guide at the operating frequency from said oneend of said first wave guide and second wave switching means comprisinga second resonant aperture device in said thirdwave guide disposedsubstantially an integral number of half wave lengths in the guide atsaid operating frequency from said one end of said first wave guide, andmeans for selectively providing ionization of the gas in the aperturesof said first and said second switching 'means providing selectiveintroduction of asubstantially infinite impedance to said waves in thecorresponding one of said second and said third wave guides.

2. In combination, a firstultra-high frequency means for introducingultra-high irequency waves into said first guide, second and third waveguides connected in branched operative relation to one end of said firstwave guide, first wave switching means comprising a first resonantchamber in said second wave guide disposed substantially an integralnumber of half wave lengths in the guide at the operating frequency fromsaid one end of said first wave guide and second wave switching meanscomprising a second resonant chamber in said third wave guide disposedsubstantially an integral number of half wave lengths in the guide atsaid operating frequency from said one end of said first wave guide, andmeans for selectively providing ionization of at least a portion of thegas in said resonant chambers of said first and said second switchingmeans providing selective introduction of a substantially infiniteimpedance to said waves in the corresponding one Of said second and saidthird wave guides.

3. In combination, a first ultra-high frequency wave guide, means forintroducing ultra-high frequency waves into said first guide, second andthird wave guides connected in branched operative relation to one end ofsaid first wave guide, first wave switching means comprising a firstresonant chamber in said second wave guide disposed substantially anintegral number of half wave lengths in the guide at the operatingfrequency from said one end of said first wave guide and second waveswitching means comprising a second resonant chamber in said third waveguide disposed substantially an integral number of half wave lengths inthe guide at said operating frequency from said one end of said firstwave guide, and means including an externally excited gaseous dischargetube disposed in each of said resonant chambers for selectivelyproviding ionization of at least a portion of the gas in said resonantchambers of said first and said second switching means providingselective introduction of a substantially infinite impedance to saidwaves in the corresponding one of said second and said third waveguides.

4. Apparatus of the type described in claim 2 including tuning means forsaid resonant chambers.

5. Apparatus of the type described in claim 2 including fixed aperturedevices between said wave guides and said resonant chambers forcontrolling the selectivity characteristics of said chambers.

6. In combination, a first-ultra-high frequency wave guide, means forintroducing ultra-high frequency waves into said first guide, second andthird wave guides connected in branched operative relation to one end ofsaid first wave guide, first wave switching means comprising a firstresonant aperture device in said second wave guide disposedsubstantially an integral number of half wave lengths in the guide atthe operating frequency from said one end of said first wave guide andsecond wave switching means comprising a second resonant aperture devicein said third wave guide disposed substantially an integral number ofhalf wave lengths in the guide at said operating frequency from said oneend of said first wave guide, and means including a keying generator forselectively providing ionization of the gas in the apertures of saidfirst and said second switching means providing selective introductionof a substantially infinite impedance frequency waves into said firstguide, second and third wave guides connected in branched operativerelation to one end of saidfirst wave guide, first wave switching meanscomprising a first resonant chamber in said second wave guide disposedsubstantially an integral number of half wave lengths in the guide atthe operating frequency from said one end of said first wave guide andsecond wave switching means comprising a secondresonant chamber in saidthird wave guide disposed substantially an integral number of half wavelengths in the guide at said operating frequency from said one end ofsaid first wave guide, and means including separate externally excitedgaseous discharge tubes in each of said chambers for adjustingselectively the resonant characteristics of said resonant chambers ofsaid first and said second switching means providing selectiveintroduction of a substantially infinite impedance to said waves in thecorresponding one of said second and said third wave guides.

10. In combination, a first ultra-high frequency wave guide, means forintroducing ultra high frequency waves into said first guide, second andthird wave guides connected in branched operative relation to one end ofsaid first wave guide, first wave switching means comprising a firstresonant chamber in said second wave guide disposed substantially anintegral number of half wave lengths in the guide at the operatingfrequency from said one end of said first wave guide and second waveswitching means comprising a second resonant chamber in said third waveguide disposed substantially an integral number of half wave lengths inthe guide at said operating frequency from said one end of said firstwave guide, and means including movable dielectric elements in each ofsaid resonant chambers for adjusting selectively the resonantcharacteristics of said resonant chambers of said first and said secondswitching means providing selective introduction of a substantiallyinfinite impedance to said waves in the corresponding one of said secondand said third wave guides.

WILLIAM D. HERSHBERGER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

